Tube bird feeders are well known in the art. They have received a high degree of acceptance due to the fact that they are relatively inexpensive.
One of the problems associated with all types of bird feeders is cleanliness. Unless proper design is used, the seed can, over a period of time, become mouldy. It is also subject to contamination by bird droppings. If proper care is not exercised, this can lead to illness among the bird population using the feeder.
Since the tube bird feeder is relatively inexpensive, it is usually manufactured in a sealed arrangement with access to the various components being difficult if not impossible.